Comprehensive reutilization of iron in iron ore tailings: preparation and characterization of magnetic flocculants

A large number of iron ore tailings (IOTs) are produced in steel industry, posing threat to the environment during its storage and disposal. To effectively reutilize Fe in IOTs, we propose a comprehensive utilization scheme: (1) most Fe in IOTs is extracted by concentrated hydrochloric acid to form FeCl₃ flocculants; (2) after separation from the FeCl₃ flocculants, a small amount of Fe is absorbed on the residue solids, which is further washed out to synthesize micron Fe₃O₄ as magnetic seeds. Results show that the as-synthetic FeCl₃ flocculants meet the product standard for FeCl₃ flocculants in China (GB/T 4482-2018) after a series of treatments including rotary evaporation, neutralization, and dilution and have comparable performance with commercial polyaluminum chloride (PAC) and polyaluminum ferric chloride (PAFC). Moreover, the addition of synthetic superparamagnetic Fe₃O₄ (as magnetic seeds) doubled the flocculation rate compared with as-synthetic FeCl₃ flocculants alone. Finally, the reutilization of Fe in IOTs can create a direct economic value of ¥ 1.27/kg IOTs, and produce 745 g high-silicon residues for further reutilization, which indicates that our comprehensive utilization scheme is of great application potential.